| Reference database and method for determining spectra using measurements from an led color sensor, and method of generating a reference database -> Monitor Keywords |
|
|
 
Reference database and method for determining spectra using measurements from an led color sensor, and method of generating a reference databaseRelated Patent Categories: Data Processing: Database And File Management Or Data Structures, Database Or File Accessing, Query Processing (i.e., Searching), Query Augmenting And Refining (e.g., Inexact Access)Reference database and method for determining spectra using measurements from an led color sensor, and method of generating a reference database description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070203905, Reference database and method for determining spectra using measurements from an led color sensor, and method of generating a reference database. Brief Patent Description - Full Patent Description - Patent Application Claims
INCORPORATION BY REFERENCE [0001] This is a Division of application Ser. No. 10/758,096, filed Jan. 16, 2004. The disclosure of the prior application is hereby incorporated by reference herein in its entirety. Cross-reference and incorporation by reference are made to the following copending and commonly assigned U.S. patent applications and/or the following U.S. patents: U.S. Pat. Nos. 6,584,435, 6,587,793, 6,556,932, 6,449,045, 6,556,300, 6,567,170, 6,621,576, 6,603,551 and U.S. patent Ser. No. 09/941,858. BACKGROUND OF THE INVENTION [0002] 1. Field of Invention [0003] This invention relates to a reference database usable for determining spectra based on non-spectral inputs. [0004] 2. Description of Related Art [0005] Automatic in-line color calibration systems can be much more effective with an in-line color measurement system where a spectrophotometer may be mounted in the paper path of the moving copy sheets in the printer, preferably in the output path after fusing or drying, without having to otherwise modify the printer, or interfere with or interrupt normal printing, or the movement of the printed sheets in said paper path, and yet provide accurate color measurements of test color patches printed on the moving sheets as they pass the spectrophotometer. That enables a complete closed loop color control of a printer. [0006] A typical spectrophotometer gives color information in terms of measured reflectances or transmittances of light, at the different wavelengths of light, from the test surface. This spectrophotometer desirably provides distinct electric signals corresponding to the different levels of reflected light received from the respective different illumination wavelength ranges or channels. [0007] Known devices capable of providing distinct electric signals corresponding to the different levels of reflected light received from the respective different illumination wavelength ranges or channels include a grating-based spectrophotometer made by Ocean Optics Inc., LED based sensors marketed by "ColorSavvy" or Accuracy Microsensor; and other spectrophotometers by Gretag MacBeth (Viptronic), ExColor, and X-Rite (DTP41). However, those devices are believed to have significant cost, measurement time, target displacement errors, and/or other difficulties, for use in real-time printer in-line measurements. [0008] As used herein, unless otherwise specifically indicated, the term "spectrophotometer" may encompass a spectrophotometer, calorimeter, and densitometer, as broadly defined herein. The definition or use of such above terms may vary or differ among various scientists and engineers. However, the following is an attempt to provide some simplified clarifications relating and distinguishing the respective terms "spectrophotometer," "calorimeter," and "densitometer," as they may be used in the specific context of specification examples of providing components for an in-line color printer color correction system, but not necessarily as claim limitations. [0009] A typical "spectrophotometer" measures the reflectance of an illuminated object of interest over many light wavelengths. Typical prior spectrophotometers in this context use 16 or 32 channels measuring from 380 nm to 730 nm or so, to cover the humanly visible color spectra or wavelength range. A typical spectrophotometer gives color information in terms of measured reflectances or transmittances of light, at the different wavelengths of light, from the test surface. (This is to measure more closely to what the human eye would see as a combined image of a broad white light spectra image reflectance, but the spectrophotometer desirably provides distinct electrical signals corresponding to the different levels of reflected light from the respective different illumination wavelength ranges or channels.) [0010] A "calorimeter" normally has three illumination channels, red, green and blue. That is, generally, a "calorimeter" provides its three (red, green and blue or "RGB") values as read by a light sensor or detector receiving reflected light from a color test surface sequentially illuminated with red, green and blue illuminators, such as three different color LEDs or one white light lamp with three different color filters. It may thus be considered different from, or a limited special case of, a "spectrophotometer," in that it provides output color information in the trichromatic quantity known as RGB. [0011] Trichromatic quantities may be used for representing color in three coordinate space through some type of transformation. Other RGB conversions to "device independent color space" (i.e., RGB converted to conventional L*a*b*) typically use a color conversion transformation equation or a "lookup table" system in a known manner. [0012] A "densitometer" typically has only a single channel, and simply measures the amplitude of light reflectivity from the test surface, such as a developed toner test patch on a photoreceptor, at a selected angle over a range of wavelengths, which may be wide or narrow. A single illumination source, such as an IR LED, a visible LED, or an incandescent lamp, may be used. The output of the densitometer detector is programmed to give the optical density of the sample. A densitometer of this type is basically "color blind." For example, a cyan test patch and magenta test patch could have the same optical densities as seen by the densitometer, but, of course, exhibit different colors. SUMMARY OF THE INVENTION [0013] A multiple LED reflectance spectrophotometer, as in the examples of the embodiments herein, may be considered to belong to a special class of spectrophotometers which normally illuminate the target with multiple instances of narrow band or monochromatic light. Others, with wide band illumination sources, can be flashed Xenon lamp spectrophotometers, or incandescent lamp spectrophotometers. A spectrophotometer is normally programmed to give more detailed reflectance values by using more than 3 channel measurements (for example, 10 or more channel measurements), with conversion algorithms. That is in contrast to normal three channel calorimeters, which cannot give accurate, human eye related, reflectance spectra measurements, because they have insufficient measurements for that (only 3 measurements). [0014] It is desirable for a printer color control system to dynamically measure the color of test patches on the printed output media "in line", that is, while the media is still in the sheet transport or paper path of a print engine, for real-time and fully automatic printer color correction applications. [0015] For a low cost implementation of the color sensor, a multiple illuminant device is used as the illumination source, and has, for example, 8, 10, 12 or 16 LEDs. Each LED is selected to have a narrow band response curve in the spectral space. Therefore, for example, ten LEDs would correspond to ten measurements in the reflectance curve. The LEDs, or other multiple illuminant based color sensor equivalent, e.g., lasers, are switched on one at a time as, for example, the measured media is passed through a transport of a printer. The reflected light is then detected by a photodetector and the corresponding voltage integrated and normalized with a white tile. [0016] To obtain a smooth curve similar to that of a Gretag spectrophotometer, linear or cubic spline algorithms could be used, which blindly interpolate the data points without knowledge of the color space. Unfortunately, due to lack of measurements at wavelengths below 430 nm and above 660 nm (due to lack of LEDs at these wavelengths), extrapolation with 10 measurements can lead to errors. [0017] U.S. Pat. Nos. 6,584,435, 6,587,793, 6,556,932, and 6,449,045 collectively disclose various systems and methods for using the integrated sensor measurements to determine a fully populated reflectance spectra with reflectance values at specific wavelengths. Those methods and systems use a reference database in determining the spectra, and convert integrated multiple illuminant measurements from a non-fully illuminant populated color sensor into a fully populated spectral curve. As described collectively in these disclosures, the reference database is generated by measuring the reflectance spectra of some set of reference colors, with an accurate reference spectrophotometer, such as a Gretag spectrophotometer, and their corresponding LED sensor outputs, with the sensor array of a given color measuring device. In general, the more densely populated the database is, i.e., the more reference colors used, the better the resulting accuracy. Furthermore, even spacing of the reference colors in the color space gives greater accuracy. The data stored in the reference database will be referred to hereafter as the training samples. [0018] This invention relates to a reference database usable with the above-described systems, and a method for constructing the reference database, and a method of using the reference database to obtain a spectral curve. In embodiments, the database is partitioned into a plurality of clusters, and an appropriate centroid is determined for each cluster. In embodiments, the centroids are obtained by vector quantization. The training samples may be assigned to the clusters by comparing the Euclidean distance between the centroids and the sample under consideration, and assigning each sample to the cluster having the centroid with the shortest Euclidean distance. When all training samples have been assigned, the resulting structure is stored as the reference database. [0019] In embodiments, when reconstructing the spectra for new measurements from the sensor, the Euclidean distances between actual color samples under measurement and each cluster centroid are calculated. The spectra are then reconstructed using only the training samples from the cluster corresponding to the shortest Euclidean distance. By thus using only a limited number of the total training samples, the speed and accuracy of the spectral reconstruction is enhanced. [0020] These and other objects, advantages and salient features of the invention are described in or apparent from the following description of exemplary embodiments. BRIEF DESCRIPTION OF THE DRAWINGS Continue reading about Reference database and method for determining spectra using measurements from an led color sensor, and method of generating a reference database... Full patent description for Reference database and method for determining spectra using measurements from an led color sensor, and method of generating a reference database Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Reference database and method for determining spectra using measurements from an led color sensor, and method of generating a reference database patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Reference database and method for determining spectra using measurements from an led color sensor, and method of generating a reference database or other areas of interest. ### Previous Patent Application: Object verification apparatus and method Next Patent Application: Unified interactive data analysis system Industry Class: Data processing: database and file management or data structures ### FreshPatents.com Support Thank you for viewing the Reference database and method for determining spectra using measurements from an led color sensor, and method of generating a reference database patent info. IP-related news and info Results in 0.12656 seconds Other interesting Feshpatents.com categories: Novartis , Pfizer , Philips , Polaroid , Procter & Gamble , 174 |
 * Protect your Inventions * US Patent Office filing 
PATENT INFO |
|
